Manufacturing method for exposure mask, generating method for mask substrate information, mask substrate, exposure mask, manufacturing method for semiconductor device and server

ABSTRACT

There is disclosed a manufacturing method for exposure mask, which comprises acquiring a first information showing surface shape of surface of each of a plurality of mask substrates, and a second information showing the flatness of the surface of each of mask substrates before and after chucked on a mask stage of an exposure apparatus, forming a corresponding relation of each mask substrate, the first information and the second information, selecting the second information showing a desired flatness among the second information of the corresponding relation, and preparing another mask substrate having the same surface shape as the surface shape indicated by the first information in the corresponding relation with the selected second information, and forming a desired pattern on the above-mentioned another mask substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 10/087,860, filed Mar. 5,2002, now U.S. Pat. No. 6,537,844 which is incorporated herein byreference.

This application is-based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2001-164695, filed May 31,2001 the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a manufacturing method for exposuremask in semiconductor field, a generating method for mask substrateinformation, a mask substrate, an exposure mask, a manufacturing methodfor a semiconductor device and server.

2. Description of Related Art

As the semiconductor devices are miniaturized, there is a demand formicronization in the photolithographic process. Already, the devicedesign rule is as small as 0.13 μm, and the pattern dimension is about10 nm and a very severe precision is requested. As a result, recently,problems are arising in photolithography in the semiconductormanufacturing process.

The problems are about flatness of mask substrate used in thephotolithographic process as one of the factors relating to enhancementof precision in pattern forming process. That is, as the micronizationis advanced, the margin for the focus in photolithography becomessmaller, and therefore the flatness of the mask substrate can be nolonger ignored.

Accordingly, the present inventor accumulated studies about flatness ofthe mask substrate, disclosed the following.

Surface shapes of mask substrate are various, including, even in thesame flatness, convex type, concave type, saddle type and mixed type.Therefore, even if the flatness is the same, when the mask substrate isfixed on the mask stage of a wafer exposure apparatus by vacuum chuck,the mask substrate may be largely deformed, or little deformed, orinversely the flatness of the mask substrate may be improved, dependingon the conformity with the mask stage or vacuum chuck.

This is because the flatness of the mask substrate after chucked dependson the surface shape of the mask substrate before fixed, and also varieswith the part of the mask substrate where the mask substrate is chuckedby the vacuum chuck even in the same mask substrate. Depending on thesurface shape of the mask substrate, the flatness of the mask substratemay be largely degraded by chucking the mask substrate on the mask stageof the wafer exposure apparatus.

It has become found that the product yield was lowered whensemiconductor devices were manufactured by using an exposure maskobtained by forming a pattern on such mask substrate with low flatness.

The inventor compared the flatness of mask substrate before and afterchucking the mask substrate on the mask stage of the wafer exposureapparatus, and confirmed that the flatness of the mask substrate wasdegraded after chucked depending on the surface shape of the masksubstrate, and found that such degraded flatness was a major cause tolower the product yield.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda manufacturing method for exposure mask comprising:

acquiring a first information showing surface shape of surface of eachof a plurality of mask substrates, and a second information showing theflatness of the surface of each of mask substrates before and afterchucked on a mask stage of an exposure apparatus;

forming a corresponding relation of each mask substrate, the firstinformation and the second information;

selecting the second information showing a desired flatness among thesecond information of the corresponding relation, and preparing anothermask substrate having the same surface shape as the surface shapeindicated by the first information in the corresponding relation withthe selected second information; and

forming a desired pattern on the another mask substrate.

According to a second aspect of the present invention, there is provideda manufacturing method for exposure mask comprising:

selecting a second information showing a desired flatness among thesecond information of relations each between a first information showinga surface shape of a surface of each of a plurality of mask substratesand the second information showing a flatness of the surface of eachmask substrate before and after chucked on a mask stage of an exposureapparatus, and preparing another mask substrate having the same surfaceshape as the surface shape indicated by the first information in thecorresponding relation with the selected second information; and

forming a desired pattern on the another mask substrate.

According to a third aspect of the present invention, there is provideda manufacturing method for exposure mask comprising:

acquiring information showing a surface shape of surface of each of aplurality of mask substrates;

forming a corresponding relation between each of the mask substrates andthe information;

selecting the information showing a convex surface shape from thecorresponding relation of the mask substrates, and selecting the masksubstrate in the corresponding relation with the selected informationfrom the plurality of mask substrates; and

forming a desired pattern on the selected mask substrate.

According to a fourth aspect of the present invention, there is provideda generating method for mask substrate information comprising:

acquiring a first information showing a surface shape of surface of eachof a plurality mask substrates, and a second information showing aflatness of the surface of each of the mask substrates before and afterchucked on a mask stage of an exposure apparatus; and

storing the first information and second information of each of the masksubstrates in a corresponding relation.

According to a fifth aspect of the present invention, there is provideda generating method for mask substrate information comprising:

acquiring information showing a surface shape of a surface of each of aplurality of mask substrates; and

storing the information showing a convex surface shape of the surface ofeach of a plurality of mask substrates from the acquired information anda corresponding mask substrate.

According to a sixth aspect of the present invention, there is provideda mask substrate comprising:

a substrate having a surface; and

a light shielding material layer configured to cover the surface of thesubstrate,

wherein a surface shape of a peripheral region of the surface of thesubstrate is lower in height than the surface of the central portion ofthe surface of the substrate toward a peripheral edge of the substrate.

According to a seventh aspect of the present invention, there isprovided an exposure mask comprising:

a substrate having a surface; and

a light shielding material pattern formed on the surface of thesubstrate,

wherein a surface shape of a peripheral region is lower in height than asurface of a central region of the surface of the substrate toward aperipheral edge of the substrate.

According to an eighth aspect of the present invention, there isprovided a manufacturing method for a semiconductor device comprising:

chucking an exposure mask manufactured by a manufacturing method forexposure mask according to the above-mentioned first aspect, on a maskstage of an exposure apparatus;

illuminating the pattern formed on the exposure mask by a lightingoptical system, and focusing an image of the pattern on a layer formedon a substrate by a projecting optical system; and

patterning the layer based on the image to form a corresponding patternwhich forms a semiconductor device.

According to a ninth aspect of the present invention, there is provideda manufacturing method for a semiconductor device comprising:

chucking an exposure mask according to the above-mentioned seventhaspect on a mask stage of an exposure apparatus; and

illuminating the pattern formed on the exposure mask by a lightingoptical system, and focusing an image of the pattern on a layer formedon a substrate by a projecting optical system; and

patterning the layer based on the image to form a corresponding patternwhich forms a semiconductor device.

According to a tenth aspect of the present invention, there is provideda server comprising:

a processing device which processes storing a page including informationshowing a corresponding relation between a first information showing asurface shape of a surface of each of a plurality of mask substrates andthe second information showing a flatness of the surface of each masksubstrate before and after chucked on a mask stage of an exposureapparatus;

a processing device which processes accepting a request messagecorresponding to the page from a client;

a processing device which processes transmitting the page in a formatdisplayable at the client side; and

a processing device which processes accepting an application message ofthe mask substrate from the client having the page transmitted.

According to an eleventh aspect of the present invention, there isprovided a manufacturing method for exposure mask comprising:

acquiring a first information showing a surface shape of a surface ofeach of a plurality of mask substrates, and a second information showingflatness of the surface of each of mask substrates after chucked on amask stage of an exposure apparatus obtained by simulation on the basisof flatness of the surface of each of the mask substrates measured by aflatness measuring apparatus and a structure of a mask chuck of theexposure apparatus;

forming a corresponding relation of each mask substrate, the firstinformation and the second information;

selecting the second information showing a desired flatness among thesecond information of the corresponding relation, and preparing anothermask substrate having the same surface shape as the surface shapeindicated by the first information in the corresponding relation withthe selected second information; and

forming a desired pattern on the another mask substrate.

According to a twelfth aspect of the present invention, there isprovided a manufacturing method for exposure mask comprising:

selecting a second information showing a desired flatness among thesecond information of corresponding relations each between a firstinformation showing a surface shape of a surface of each of a pluralityof mask substrates and the second information showing flatness of thesurface of each of mask substrates after chucked on a mask stage of anexposure apparatus obtained by simulation on the basis of flatness ofthe surface of each of the mask substrates measured by a flatnessmeasuring apparatus and a structure of a mask chuck of the exposureapparatus, and preparing another mask substrate having the same surfaceshape as the surface shape indicated by the first information in thecorresponding relation with the selected second information; and

forming a desired pattern on the another mask substrate.

According to a thirteenth aspect of the present invention, there isprovided a manufacturing method for exposure mask comprising:

acquiring a first information showing a surface shape of a surface of amask substrate;

acquiring a second information showing flatness of the surface of themask substrate after chucked on a mask stage of an exposure apparatusobtained by simulation on the basis of the surface shape of the surfaceof the mask substrate shown by the first information and a structure ofa mask chuck of the exposure apparatus;

judging whether or not the flatness of the surface of the mask substrateis conformed to a specification; and

processing the mask substrate to form an exposure mask if it is judgedthat the flatness is conformed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a flowchart showing the flow of a manufacturing method for anexposure mask according to a first embodiment of the present invention;

FIG. 2A is a plan view of a surface of a mask substrate, for explaininga first region 1 and a second region 2 of the surface of the masksubstrate;

FIG. 2B is a schematic cross sectional view of the mask substrate shownin FIG. 2A, for explaining the cross section of the first region 1 ofthe mask substrate;

FIG. 2C is another schematic cross sectional view of the mask substrateshown in FIG. 2A, for explaining the cross section of the first region 1of the mask substrate;

FIG. 2D is a schematic cross sectional view of the mask substrate shownin FIG. 2A, for explaining the cross section of the second region 2 ofthe mask substrate;

FIG. 3A is a schematic perspective view of the surface of the masksubstrate shown in FIG. 2A, for explaining a surface shape of the firstregion 1 of the surface of the mask substrate;

FIG. 3B is a schematic perspective view of the surface of the masksubstrate shown in FIG. 2A, for explaining another surface shape of thefirst region 1 of the surface of the mask substrate;

FIG. 3C is a schematic perspective view of the surface of the masksubstrate shown in FIG. 2A, for explaining a further surface shape ofthe first region 1 of the surface of the mask substrate;

FIG. 3D is a schematic perspective view of the surface of the masksubstrate shown in FIG. 2A, for explaining a still further surface shapeof the first region 1 of the surface of the mask substrate;

FIG. 4 is a flowchart showing the flow of a manufacturing method for anexposure mask according to a third embodiment of the present invention;

FIG. 5 is a flowchart showing the flow of a manufacturing method for anexposure mask according to a fourth embodiment of the present invention;and

FIG. 6 is a system diagram schematically showing a server according to asixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, preferred embodiments of the presentinvention are described below.

(First Embodiment)

FIG. 1 is a flowchart showing the flow of a manufacturing method forexposure mask according to a first embodiment of the invention.

Eleven mask substrates A to K are prepared, each of which comprises aquartz substrate of 152 mm square and about 6 mm on which a lightshielding material layer is formed to cover the quartz substrate.

A surface of each mask substrate is measured by a flatness measuringapparatus (Nidek), and a surface shape and flatness of the surface ofeach of the mask substrate before chucked on a mask stage of an exposureapparatus by vacuum chuck is obtained (step S1).

As shown in FIG. 2A, a first region 1 of 142 mm square was measured. Thefirst region 1 is a pattern forming region in which a pattern orpatterns are formed and excludes the peripheral region of the surface ofthe mask substrate.

In this embodiment and following embodiments, that the shape of thesurface of the first region 1 is convex means that the shape of thesurface of the first region 1 is convex upward from line L1 connectingthe both ends of the first region 1, as shown in FIG. 2B. Similarly,that the shape of the surface of the first region 1 is concave meansthat the shape of the surface of the first region 1 is concave downwardfrom line L1 connecting the both ends of the first region 1, as shown inFIG. 2C. FIG. 3A is a schematic perspective view of the surface of themask substrate shown in FIG. 2A, in which a surface shape of the firstregion 1 of the surface of the mask substrate is convex upward, and FIG.3B is a schematic perspective view of the surface of the mask substrateshown in FIG. 2A, in which a surface shape of the first region 1 of thesurface of the mask substrate is concave downward;

Also, in this embodiment and following embodiments, that the shape ofthe surface of the second region 2 is convex means that the height ofthe surface of the second region 2 goes down toward the peripheralregion of the surface of the mask substrate, as shown in FIG. 2D.Similarly, that the shape of the surface of the second region 2 isconcave means that the height of the surface of the second region 2 goesup toward the peripheral region of the surface of the mask substrate,also as shown in FIG. 2D.

The second region 2 will be more described in a second embodiment of thepresent invention.

Following the flatness measurement step, on the basis of the obtainedmeasurement result, the mask substrates A to K are classified into typesof the surface shape of each of the mask substrates (step S2). Theclassified results are shown in Table 1. As shown in table 1, on thebasis of the measurement result, the mask substrates were classifiedinto four types (first information) of surface substrate thereof, thatis, convex shape type, concave shape type, saddle shape type, andsemi-cylindrical shape type. Measurements of flatness (secondinformation) of the first region before fixed on the mask stage, i.e.before chucked by vacuum chuck, settled in a range of 0.4 μm to 0.5 μm.

TABLE 1 Flatness Flatness before after Mask chucked Surface shapechucked substrate (μm) before chucked (μm) A 0.5 convex 0.4 B 0.4 convex0.4 C 0.45 convex 0.4 D 0.5 concave 0.8 E 0.5 concave 1.0 F 0.4 saddle0.9 G 0.5 saddle 0.9 H 0.4 semi-cylindrical 0.4 I 0.5 semi-cylindrical0.4 J 0.5 semi-cylindrical 0.2 (90-degree rotation) K 0.5semi-cylindrical 0.3 (90-degree rotation)

Next, the mask substrates are sequentially fixed by vacuum chuck on themask stage of an ArF wafer exposure apparatus (Nikon), and the flatnessof surface of each mask substrate after chucked by vacuum chuck ismeasured (step S3). Herein, the first region 1 of 142 mm square wasmeasured. After the measurement step, the corresponding relation in eachof the mask substrate A to K, of the type of surface shape and flatnessbefore and after chucked by vacuum chuck, is tabled as shown in Table 1(step S4).

As understood from Table 1, the flatness of the mask substrates A to Cof the convex type surface shape after chucked is same or slightlybetter as compared with that before chucked, however in the masksubstrates D to G of concave or saddle type surface shape after chucked,the flatness was notably degraded.

The mask substrates H and I of the semi-cylindrical type surface shapewere arranged on the mask stage in a predetermined direction with regardto the chuck. On the other hand, the mask substrates J and K of thesemi-cylindrical type surface shape were arranged on the mask stage in adirection changed by an angle of 90 degree from the predetermineddirection so that the portion of the mask substrate to be chucked ischanged.

It was found from the measurement result that the flatness ofsemi-cylindrical type mask substrates H to K after chucked is changeddepending on the direction in which the mask substrates are arrangedwith regard to the chuck, as shown in Table 1.

In other words, it was found from the measurement result that theflatness of semi-cylindrical type mask substrates H to K after chuckedis changed depending on the part of the mask substrate where the masksubstrates are chucked by vacuum chuck.

More specifically, it was found from the measurement result that whenthe mask substrates, as in mask substrates H and I, of thesemi-cylindrical type surface shape were arranged on the mask stage inthe predetermined direction, then the side of arc of the mask substratecontacts a chuck of the mask stage and thus the flatness of the masksubstrates after chucked is same or slightly better as compared withthat before chucked. On the other hand, it was found from themeasurement result that when the mask substrates, as in mask substratesJ and K, of the semi-cylindrical type surface shape were arranged on themask stage in a direction changed by an angle of 90 degree from thepredetermined direction, then the side of the arc of the mask substratedoes not contact the chuck of the mask stage and thus the flatness ofthe mask substrates after chucked is 0.3 μm or less and greatlyimproved. In the mask substrates A to G of other surface shapes, nomeasurement data when the mask substrates A to G are arranged in theangle of 90 degree changed direction is listed in Table 1 because it wasfound that the flatness was not improved in the change of angle of 90degree.

From the mask substrates A to K in which the surface shape and flatnessof the first region 1 before and after chucked by vacuum chuck have beenalready acquired, a mask substrate having the flatness conforming to thespecification is selected and another mask substrate having the sametypes of surface shape as the selected substrate is prepared (step S5).Here, an example in which a mask substrate having the same type ofsurface shape as mask substrate J is prepared as the prepared anothermask substrate is explained.

These mask substrates A to K and the prepared another mask substrate areformed so that the flatness in the pattern forming region may settlewithin the prescribed specification, and the difference in the surfaceshape is due to fluctuations.

Next, a resist is applied on the prepared another mask substrate.

After that, the known manufacturing method for exposure mask follows.That is, a desired pattern is drawn on the resist layer on the masksubstrate by using an electron beam drawing apparatus. By developing theresist layer, a resist pattern is formed, and using the resist patternas a mask, a light shielding pattern is formed by etching the lightshielding material layer on the substrate by a reactive ion etchingapparatus. Then the resist pattern is removed, and the mask substratesurface is cleaned, and an exposure mask having a desired pattern isrealized (step S6). The desired pattern includes, for example, a circuitpattern, or a circuit pattern and a positioning pattern.

The exposure mask thus obtained was set on the ArF wafer exposureapparatus, and the flatness of the surface was measured, and a favorablevalue of 0.2 μm was confirmed. Thus, by performing an exposure method inwhich the exposure mask of such high flatness is fixed on the mask stageof the exposure apparatus, the pattern formed on the exposure mask isilluminated by a lighting optical system, and the pattern image isfocused on a desired substrate (for example, a resist coated substrate)by a projection optical system, the margin of focus in wafer exposure isremarkably increased, and the yield of semiconductor products such asDRAM is substantially enhanced.

In this manner, this embodiment realizes an effective manufacturingmethod for exposure mask in order to solve the disadvantage ofdegradation of product yield due to degradation of flatness of masksubstrate after chucked on the mask stage of the wafer exposureapparatus.

The mask substrates A to K, or the prepared another mask substrate mayhave a positioning mark formed in advance. Manner for chucking the masksubstrate on the mask stage is not limited to vacuum chuck.

(Second Embodiment)

In the first embodiment, the surface shape and flatness are acquiredonly in the first region 1 of the surface of the mask substrate shown inFIG. 2A (step S1), however in this second embodiment, the surface shapeand flatness are acquired both in the first region 1 and second region 2of the surface of the mask substrate shown in FIG. 2A.

The first region 1 is a rectangular area of 142 mm in length of oneside, whose center is substantially the center of the surface of themask substrate, and the second region 2 surrounds the first region 1 andis a mouth-like or ring-like square region (i.e., a region excluding asmaller rectangular region from a rectangular region, with the center ofthe rectangular regions being the same) of 150 mm in length of one side.The second region 2 includes almost of the mask chucking region to befixed by vacuum chuck when setting the mask substrate on an exposureapparatus. That is, almost all of a force for chucking the masksubstrate on the mask stage is applied to the second region 2.

As an advancement from the prior art, when taking also the flatness ofthe mask chuck region into consideration, the first region 1 would beexpanded, and the flatness of the expanded first region 1 including themask chuck region would be taken into consideration.

In the ordinary mask manufacturing technology, however, it is extremelydifficult to form the entire surface of the mask substrate flat, and inpractice the flatness of the surface of the mask substrate 1 isextremely degraded at the end portion. Hence, if the first region 1 isexpanded, the measured data of flatness of the mask substrate islowered, since the flatness of the end portion of the mask substrate 1is poor, though the flatness of the central part of the mask substrateis good.

In this embodiment, accordingly, the flatness and the surface shape areacquired, in both the first region 1 including the center part of themask substrate and the second region 2 surrounding the first region 1.

The surface shape of the surface of the mask substrate comprising alight shielding material layer on a quartz substrate of 152 mm squareand about 6 mm in thickness was measured by a flatness measuringinstrument (Nidek), and thirteen mask substrates A to M different fromeach other in the flatness and surface shape of the first region andflatness and surface shape of the second region were prepared.

These thirteen mask substrates A to M were sequentially set to the ArFwafer exposure apparatus (Nikon), and the flatness and the surface shapeof both the first region 1 and the second region 2 were measured afterchucked by vacuum chuck.

Next, a corresponding relation of the type of surface shape and flatnessbefore and after chucked by vacuum chuck is made for each of the masksubstrates A to M. The relation is listed in Table 2.

TABLE 2 First region Second region (before chucked) (before chucked)First region Mask Flatness Surface Flatness Surface (after chucked)substrate (μm) shape (μm) shape Flatness (μm) A 0.3 convex 4 convex 0.3B 0.3 convex 3 concave 1.5 C 0.35 convex 4 semi- 0.6 cylindrical D 0.35convex 4 semi- 0.3 cylindrical (90-degree rotation) E 0.35 convex 4saddle 1.0 F 0.35 concave 4 convex 0.3 G 0.35 concave 4 convex 0.8 H0.35 concave 4 semi 0.8 cylindrical I 0.35 concave 4 semi- 0.4cylindrical (90-degree rotation) J 0.35 concave 4 saddle 0.9 K 0.5saddle 3 saddle 1.0 L 0.5 semi- 3 semi- 0.9 cylindrical cylindrical M0.4 semi- 3 semi- 0.4 cylindrical cylindrical (90-degree rotation)

The surface shape of the first and second regions of the thirteen masksubstrates A to M were classified into four types, that is, convex type,concave type, saddle type, and semi-cylindrical type. In the masksubstrate A of the simple convex shape, the surface shapes of the firstregion 1 and the second region 2 were both convex. In the mask substrateB shaped like brimmed hat, the surface shape was convex in the firstregion 1 and concave in the second region 2.

As listed in Table 2, the mask substrates degraded in surface shape ofthe first region 1 before and after chucked by vacuum chuck are thosehaving the second region 2 in the convex and saddle type surface shape.The mask substrates C, D, H, I, L, and M having semi-cylindrical typesurface shape indicated different results depending on the direction inwhich the mask substrates are arranged on the mask stage.

More specifically, it was found from the measurement result that whenthe mask substrates of the semi-cylindrical type surface shape werearranged on the mask stage in the predetermined direction, then the sideof arc of the mask substrate contacts a chuck of the mask stage and thusthe flatness of the mask substrates after chucked is degraded ascompared with that before chucked. On the other hand, it was found fromthe measurement result that when the mask substrates of thesemi-cylindrical type surface shape were arranged on the mask stage in adirection changed by an angle of 90 degree from the predetermineddirection, then the side of the arc of the mask substrate does notcontact the chuck of the mask stage and thus the flatness of the masksubstrates after chucked is 0.4 μm or less and the flatness of almost ofthe mask substrates are improved.

The flatness of the first region 1 after chucked by vacuum chuck wasconfirmed to be nearly in no relation to the surface shape of the firstregion 1 before chucked. That is, the change of the surface shape of themask substrate before and after chucked by vacuum chuck is determinedmostly by the surface shape of the second region 2.

Further, although the flatness of the second region 2 is greatly lowerthan the flatness of the first region 1, in the case where the surfaceshape of the second region 2 is convex, the surface shape of the firstregion 1 of the mask substrate-is hardly changed after chucked by vacuumchuck.

Hence, for each of the plural mask substrates, by forming thecorresponding relation between the type of surface shape of the firstregion 1 and the second region 2 and the flatness before and afterchucked by vacuum chuck, it becomes unnecessary to extend the firstregion 1 of the mask substrate more than necessary in order to determinethe flatness of the mask chuck region, and the flatness of the firstregion is not required to be stricter than necessary and may be set at arealistic value. Further by taking the surface shape of the secondregion 2 into consideration, a mask substrate smaller in change offlatness before and after chucked by vacuum chuck can be more securelyselected.

From the mask substrates A to M in which the types of surface shape andflatness of the first region 1 and the second region 2 before and afterchucked by vacuum chuck have been already acquired, a mask substratehaving the flatness conforming to the specification is selected andanother mask substrate having the same types of surface shape as theselected substrate is prepared (step S5). Here, a mask substrate havingthe same type of surface shape as mask substrate F (concave in firstregion 1 and convex in second region 2) is prepared as the preparedanother mask substrate. When this another mask substrate was measured,the flatness of the first region 1 was 0.3 μm or less and the flatnessof the second region 2 was 4 μm or less.

Next, a resist is applied on the flesh mask substrate.

After that, the known manufacturing method for exposure mask follows.That is, a desired pattern is drawn on the resist layer on the masksubstrate by using an electron beam drawing apparatus. By developing theresist layer, a resist pattern is formed, and using the resist patternas a mask, a light shielding pattern is formed by etching the lightshielding material layer on the substrate by a reactive ion etchingapparatus. Then the resist pattern is removed, and the mask substratesurface is cleaned, and an exposure mask having a desired pattern isrealized. The desired pattern includes, for example, a circuit pattern,or a circuit pattern and a positioning pattern.

The exposure mask thus obtained was set on the ArF wafer exposureapparatus, and the flatness of the first region 1 was measured, and afavorable value of 0.2 μm was confirmed. Thus, by performing an exposuremethod in which the exposure mask of such high flatness is fixed on themask stage of the exposure apparatus, the pattern formed on the exposuremask is illuminated by a lighting optical system, and the pattern imageis focused on a desired substrate (for example, a resist coatedsubstrate) by a projection optical system, the margin of focus in waferexposure is remarkably increased, and the yield of semiconductorproducts such as DRAM is substantially enhanced.

In this manner, as with the first embodiment, this embodiment realizesan effective manufacturing method for exposure mask in order to solvethe disadvantage of degradation of product yield due to degradation offlatness of mask substrate after chucked on the mask stage of the waferexposure apparatus.

The mask substrates A to M, or the prepared another mask substrate mayhave a positioning mark formed in advance. Manner for chucking the masksubstrate on the mask stage is not limited to vacuum chuck.

As understood from Table 2, in the case of convex surface shape of thesecond region 2, the flatness of the first region 1 after chucked byvacuum chuck is excellent, and hence a mask substrate or exposure maskhaving a convex surface shape of the second region may be prepared andused.

The mask substrate or exposure mask having such surface shape in thesecond region can be obtained, for example, by making use of the factthat the polishing rate is higher in the central region (inside region)of a quartz substrate than in the peripheral region thereof.Specifically, it is obtained by polishing the surface of the quartzsubstrate longer than in conventional by using a polishing device.Thereafter, according to the known method, a light shielding film isformed to form a mask substrate, and then patterning of the lightshielding film is performed to form an exposure mask.

Thus, as with the first embodiment, by performing an exposure method inwhich the exposure mask having the second region 2 with thepredetermined surface shape (concave shape in the example) is fixed onthe mask stage of the exposure apparatus, the pattern formed on theexposure mask is illuminated by a lighting optical system, and thepattern image is focused on a desired substrate (for example, a resistcoated substrate) by a projection optical system, the margin of focus inwafer exposure is remarkably increased, and the yield of semiconductorproducts such as DRAM is substantially enhanced.

Conventionally, in order to form the entire surface as flat as possible,the quartz substrate was polished. However, in order to make thedifference in polishing rate less distinctive, it was not controlled toextend the polishing time longer. Therefore, if the surface shape of thesecond region becomes convex or concave due to fluctuation in polishing,its degree is obviously smaller than that of the mask substrate orexposure mask obtained by this embodiment.

(Third Embodiment)

In this embodiment, surface shapes of the surfaces of mask substratescorresponding to surface shapes of the surfaces of mask substrates afteractually chucked by vacuum chuck are acquired by utilizing a simulation.

First, the surface shape of the surface of each of the mask substratesformed of a light shielding material layer on a quartz substrate of 152mm square in size and about 6 mm in thickness was determined bymeasuring the flatness of the first region 1 (FIG. 2A) using theflatness measuring apparatus (Nidek), and thirteen mask substrates A toM different from each other in the flatness and surface shape wereprepared.

Next, on the basis of the structure of the mask chuck of the ArF waferexposure apparatus (Nikon) and the flatness of the surfaces of the masksubstrates A to M already acquired, the surface shape of the surface ofeach of the mask substrates A to M at the time when the mask substratesA to M were sequentially fixed on the mask stage of the ArF waferexposure apparatus by the vacuum chuck using a finite element methodwere acquired by utilizing a simulation. The finite element method maybe replaced with any analytical method.

Subsequently, in order to confirm whether or not the simulation resultis satisfied, the mask substrates A to M were actually and sequentiallyfixed on the above-described ArF wafer exposure apparatus by vacuumchuck, and the surface shape of the surface of each of the respectivemask substrates after chucked by the vacuum chuck were measured. As aresult, it was confirmed that as indicated in Table 3, in almost all ofthe mask substrates A to M, there is only the difference of 0.1 μm orless between the flatness of the surface of each of the mask substratesA to M obtained by the simulation and the flatness of the surface ofeach of the mask substrates A to M obtained by the measurement using theabove-mentioned flatness measuring apparatus on which these masksubstrates A to M have been actually set.

TABLE 3 Flatness Flatness Measurement data of mask by after substratesurface simulation chucked Flatness Flatness Flatness Mask substrate(μm) Surface shape (μm) (μm) A 0.3 convex 0.3 0.3 B 0.3 convex 1.5 1.5 C0.35 convex 0.6 0.6 D 0.35 convex 0.3 0.3 E 0.35 convex 1.0 1.0 F 0.35concave 0.5 0.3 G 0.35 concave 0.7 0.8 H 0.35 concave 0.8 0.8 I 0.35concave 0.5 0.4 J 0.35 concave 0.9 0.9 K 0.5 saddle 1.3 1.0 L 0.5semi-cylindrical 0.9 0.9 M 0.4 semi-cylindrical 0.4 0.4

This indicates that, upon preparing the corresponding relationshipbetween the surface shape and the flatness each of the mask substratesbefore and after chucked the mask substrates by vacuum chuck, theflatness after the fixation by vacuum chuck can be replaced with theflatness acquired by the simulation.

From this result, it was understood that it is capable of predicting thesurface shapes of the surfaces of the mask substrates at the time whenthe mask substrates have been actually set on the wafer exposureapparatus, by first measuring the flatness and the surface shape of thesurface of each of the mask substrates before chucking the masksubstrates by using the flatness measuring apparatus (Nidek) and thensimulating the surface shapes of the surfaces of the mask substrates atthe time when the mask substrates were sequentially fixed on the maskstage of the exposure apparatus by the vacuum chuck, on the basis of theflatness of the surface of each of the mask substrates already acquiredby the flatness measuring apparatus and the mask chuck structure of theexposure apparatus. Thus, the flatness and the surface shape of thesurface of each of the mask substrates can be controlled with aremarkably higher precision comparing to the conventional ones.

FIG. 4 is a flowchart showing the flow of a method of manufacturing anexposure mask pertaining to the third embodiment of the presentinvention. In the flowchart of FIG. 4, in the Step S3, the surface shapeof the surface of each of the mask substrates at the time when the masksubstrates have been fixed by the vacuum chuck are acquired by utilizinga simulation. Then, in the Step S4, the corresponding relationshipbetween the flatness and the surface shape of each of the mask substrateacquired using the flatness measuring apparatus and the flatness and thesurface shape of each of the mask substrate acquired by utilizing thesimulation is prepared. Referring to the Steps S1, S2 and S5 to S6,these Steps are similar to the Steps of the flowchart of FIG. 1.

Next, in step S5, another mask substrate whose surface shape of thesurface has been measured by the flatness measuring apparatus and whosesurface shape of the surface at the time when the mask substrate hasbeen fixed on the mask stage of the exposure apparatus by the vacuumchuck has been determined to be 0.2 μm by utilizing the simulation, wasprepared besides the above-described mask substrates A to M.

Next, at step S6, resist was coated on the prepared another masksubstrate.

And then, the processes of manufacturing an exposure mask by the wellknown methods are followed. Specifically, a desired pattern is depictedon the resist on the prepared another mask substrate by an electron beamdepicting apparatus. Subsequently, the resist is developed to form aresist pattern, and next, with the resist pattern being made as a mask,a light shielding material pattern (mask pattern) is formed bypatterning the light shielding material layer of the mask substrate byusing a reactive ion etching apparatus. Then, the resist pattern isremoved, subsequently, the washing of the mask substrate surfaces isperformed, and an exposure mask on which the desired mask pattern hasbeen formed is completed. When this exposure mask was actually set onthe ArF wafer exposure apparatus and the surface shape of the surfaceand the flatness of the flesh mask substrate was measured using theflatness measuring apparatus it was confirmed that the flatness is 0.2μm as simulated and it is excellent flatness. Thus, by performing anexposure method in which the exposure mask of such high flatness isfixed on the mask stage of the exposure apparatus, the pattern formed onthe exposure mask is illuminated by a lighting optical system, and thepattern image is focused on a desired substrate (for example, a resistcoated substrate) by a projection optical system, the margin of focus inwafer exposure is remarkably increased, and the yield of semiconductorproducts such as DRAM is substantially enhanced.

In this manner, as with the first embodiment and the second embodiment,this embodiment realizes an effective manufacturing method for exposuremask in order to solve the disadvantage of degradation of product yielddue to degradation of flatness of mask substrate after chucked on themask stage of the wafer exposure apparatus.

The mask substrates A to M, or the prepared another mask substrate mayhave a positioning mark formed in advance. Manner for chucking the masksubstrate on the mask stage is not limited to vacuum chuck.

In the respective embodiments described above, for example, the waferexposure apparatus may not be an ArF wafer exposure apparatus. Moreover,after the formation of a mask pattern, the flatness of the surfaces ofthe mask substrates may be further measured, and the surface shapes ofthe surfaces of the mask substrates at the time when the mask substrateshave been set on the exposure apparatus may be acquired by utilizing thesimulation based on the measured data. Owing to this, the deformationsof the surfaces of the mask substrates generated at the time when themask patterns have been formed are incorporated into the acquisitionresults performed by the simulation, therefore, the surface shapes ofthe surfaces of the mask substrates are capable of being detected with ahigher precision. Furthermore, the mask is not limited to a mask for ArFand a mask for KRF, for example, it can be also applied as a reflectortype mask for vacuum ultraviolet ray exposure, a mask for x-rayexposure, a mask for electron beam exposure or the like.

(Fourth Embodiment)

In this embodiment, the surface shape of the surface of a mask substratecorresponding to the surface shape of the surface of the mask substrateafter actually chucked by a vacuum chuck are acquired by utilizing asimulation.

FIG. 5 is a flowchart showing the flow of a method of manufacturing anexposure mask pertaining to the this embodiment of the presentinvention.

First, in step S1, the surface shape of the surface of the masksubstrate formed of a light shielding material layer on a quartzsubstrate of 152 mm square in size and about 6 mm in thickness wasdetermined by measuring the flatness of the first region 1 (FIG. 2A)using the flatness measuring apparatus (Nidek).

Next, in step S2, the flatness and the surface shape of the surface ofthe mask substrate at the time when the mask substrate has been fixed bythe vacuum chuck is acquired by utilizing a simulation, using a finiteelement method, based on the surface shape of the surface of the masksubstrate acquired by step S1 and a structure of a mask chuck of theexposure apparatus.

In step S3, it is judged whether or not the flatness of the masksubstrate is conformed to the specification. If it is judged that theflatness is conformed to the specification, then the process enters stepS4 in which an exposure mask is formed.

On the other hand, in step S3 if it is judged that the flatness is notconformed to the specification, then the process enters step S5 in whichthe light-shielding material layer on the quartz substrate of the masksubstrate is removed. Thereafter, the surface of the quartz substrate ispolished in step S6. In step S7, a fresh light-shielding layer is formedon the polished surface of the quartz substrate, and the process goesback to step S1.

In this manner, as with the first embodiment, the second embodiment andthe third embodiment, this embodiment realizes an effectivemanufacturing method for exposure mask in order to solve thedisadvantage of degradation of product yield due to degradation offlatness of mask substrate after chucked on the mask stage of the waferexposure apparatus.

The mask substrate may have a positioning mark formed in advance. Mannerfor chucking the mask substrate on the mask stage is not limited tovacuum chuck.

Also in this embodiment, for example, the wafer exposure apparatus maynot be an ArF wafer exposure apparatus. Moreover, after the formation ofa mask pattern, the flatness of the surface of the mask substrate may befurther measured, and the surface shape of the surface of the masksubstrate at the time when the mask substrate has been set on theexposure apparatus may be acquired by utilizing the simulation based onthe measured data. Owing to this, the deformation of the surface of themask substrate generated at the time when the mask pattern has beenformed is incorporated into the acquisition results performed by thesimulation, therefore, the surface shape of the surface of the masksubstrate is capable of being detected with a higher precision.Furthermore, the mask is not limited to a mask for ArF and a mask forKRF, for example, it can be also applied as a reflector type mask forvacuum ultraviolet ray exposure, a mask for x-ray exposure, a mask forelectron beam exposure or the like.

(Fifth Embodiment)

A generating method for mask substrate information according to a fifthembodiment of the present invention will be explained below.

In the generating method for mask substrate information according tothis embodiment, the surface shape of the surface and flatness ofsurface before and after chucked are acquired according to, for example,steps S1 to S3 of flow chart of FIG. 1 for each of eleven masksubstrates A to K of Table 1, the correspondence of the mask substrate,surface shape type and flatness are made as shown in Table 1 for each ofthe eleven mask substrates A to K, and such correspondence is stored ina personal computer (PC) or the like.

Further, the correspondence (presentation content) stored in thepersonal computer (PC) or the like may be presented. Specifically, aseal in which the presentation content is printed may be attached to acontainer holding the mask substrates A to K.

By employing such manner of presentation, it is easy to control theeffective mask substrate for solving the problem of degradation ofproduct yield due to gradation of flatness of mask substrate afterchucked on the mask stage of the wafer exposure apparatus.

Further, after step S2 of flow chart of FIG. 1, of the informationacquired at the step S2, the correspondence relation of informationshowing the convex surface shape of the surface and the correspondingmask substrate is made, and the correspondence is stored in the personalcomputer (PC) or the like, so that another different generating methodfor mask substrate information may be realized. In such a case, too, asin the above generating method for mask substrate information, bypresenting the seal or the like regarding the correspondence, the masksubstrate can be easily controlled.

The generating method for mask substrate information is explained byreferring to an example of mask substrates to K in Table 1, however themask substrate information can be similarly generating in masksubstrates A to M in Table 2.

(Sixth Embodiment)

FIG. 6 is a diagram schematically showing a server system according to asixth embodiment of the invention. In the fifth embodiment, the seal isused as an example of presentation, but in this embodiment theinformation is presented on the server (server device), so that thegenerating method for mask substrate information of the invention may beapplied in the so-called electronic-mail business.

First, a table such as Table 1, Table 2 or Table 3 showing thepresentation content is formed at a fab 11, and a page containing thetable as information is uploaded to a server 12. The server 12 storesthe page in storage medium such as a hard disk.

The server 12 is connected to plural clients (client devices) 13 throughthe internet. Instead of the internet, an exclusive line may be used. Orthe internet may be combined with an exclusive line.

The server 12 comprises a known processing device which processesacceptance of request message to the page, a known processing devicewhich processes transmission of the page in a format that can bedisplayed at the client side, and a known processing device whichprocesses acceptance of an application message of the substrate maskfrom the client 13 having the page transmitted. These known processingdevices means are formed of, for example, LAN card, storage device,server software, CPU and others, and they cooperate to process asdesired.

When accepting the request message to the page from the client 13, theserver 12 sends the necessary information to the client 13 fordisplaying a screen 14 as shown in FIG. 3 in the display of the client13. The screen 14 shows a table 15 having the content shown in Table 1,a check box 16 for selecting a desired mask substrate and checking, andan enter icon 17 for transmitting the execution of purchasing the masksubstrate checked in the check box to the server 12. The diagram showsthe table 15 having the content shown in Table 1 for the sake ofsimplicity, however, instead, a table having the content shown in Table2 or Table 2 may be used.

With this embodiment, after chucking the mask substrate on the maskstage of the wafer exposure apparatus, a mask substrate of high flatnesscan be purchased, and it realizes an effective server for solving theproblem of degradation of product yield due to degradation of flatnessof mask substrate after chucked on the mask stage.

The preferred embodiments of the invention are described herein,however, it is noted that the invention is not limited to theseembodiments. For example, although in the foregoing embodiments afavorable result was obtained in the mask substrate of convex shape, abetter result may be obtained in the mask substrate of concave shape,depending on the exposure apparatus to which the mask substrate is set.That is, the flatness of the mask substrate after vacuum chuck dependson the interrelation between the mask chuck stage and mask chucksurface, and thus the surface shape of the mask substrate to be selectedvaries with the mask chuck stage to be used.

Further, in the embodiments, the mask substrate for ArF wafer exposureapparatus is explained, however the invention may be applied in othermask substrates, such as mask substrate for KrF wafer exposureapparatus, reflection type mask substrate for vacuum ultraviolet rayexposure, mask substrate for X-ray exposure, and mask substrate forelectron beam exposure.

What is claimed is:
 1. A mask substrate comprising: a substrate having asurface, the substrate being made of a material that allows a light beamto pass through it; and a light shielding material layer configured tocover the surface of the substrate, wherein a surface of a peripheralregion of the surface of the substrate is lower in height than thesurface of the central portion of the surface of the substrate toward aperipheral edge of the substrate.
 2. The mask substrate according toclaim 1, wherein a region inside of the peripheral region is a patternforming region.
 3. The mask substrate according to claim 1, wherein partof the peripheral region is a region which apply a force for chuckingthe substrate on a mask stage of an exposure apparatus.
 4. An exposuremask comprising: a substrate having a surface, the substrate being madeof a material that allows a light beam to pass through it; and a lightshielding material pattern formed on the surface of the substrate,wherein a surface shape of a peripheral region is lower in height than asurface of a central region of the surface of the substrate toward aperipheral edge of the substrate.
 5. The exposure mask according toclaim 4, wherein the pattern is formed in a region inside of theperipheral region of the surface.
 6. The exposure mask according toclaim 4, wherein part of the peripheral region is a region which apply aforce for chucking the substrate on a mask stage of an exposureapparatus.
 7. A server comprising: a processing device which processesstoring a page including information showing a corresponding relationbetween a first information showing a surface shape of a surface of eachof a plurality of mask substrates and the second information showing aflatness of the surface of each mask substrate before and after chuckedon a mask stage of an exposure apparatus; a processing device whichprocesses accepting a request message corresponding to the page from aclient; a processing device which processes transmitting the page in aformat displayable at the client side; and a processing device whichprocesses accepting an application message of the mask substrate fromthe client having the page transmitted.